Prakash N, Fehr S, Mohr E, Richter D
Institut für Zellbiochemie und Klinische Neurobiologie, Universität Hamburg, Germany.
Eur J Neurosci. 1997 Mar;9(3):523-32. doi: 10.1111/j.1460-9568.1997.tb01629.x.
Transcripts encoding the vasopressin precursor are located in axons and dendrites of rat hypothalamic magnocellular neurons. While the axonal vasopressin mRNA has been extensively characterized both at the biochemical and morphological level, little is known about those transcripts residing in dendrites of magnocellular neurons. As revealed by in situ hybridization at the electron microscopic level, the mRNA is located in proximal and distal dendritic segments and is exclusively confined to regions containing rough endoplasmic reticulum. These results suggest that dendrites of hypothalamic neurons may be capable of local precursor synthesis independent of that occurring in the cell somata. A heterologous system has been employed to define cis-acting elements within the vasopressin mRNA which may be involved in dendritic compartmentalization. Expression vector constructs consisting of the cytomegalovirus promoter coupled to the rat vasopressin cDNA have been injected into the cell nuclei of cultured neurons derived from embryonic rat superior cervical ganglia. Vector-encoded vasopressin transcripts were also sorted to dendrites of these neurons indicating that the molecular determinants of dendritic mRNA transport are not cell specific. Mapping of the targeting elements revealed two segments within the vasopressin mRNA that are able to confer dendritic compartmentalization to alpha-tubulin mRNA which is normally confined to the cell body.
编码血管加压素前体的转录本位于大鼠下丘脑大细胞神经元的轴突和树突中。虽然轴突血管加压素mRNA在生化和形态学水平上都已得到广泛表征，但对于大细胞神经元树突中的那些转录本却知之甚少。如电子显微镜水平的原位杂交所显示，mRNA位于树突近端和远端节段，并且仅局限于含有粗面内质网的区域。这些结果表明，下丘脑神经元的树突可能能够独立于细胞体中发生的过程进行局部前体合成。已采用异源系统来确定血管加压素mRNA中可能参与树突区室化的顺式作用元件。由与大鼠血管加压素cDNA偶联的巨细胞病毒启动子组成的表达载体构建体已被注入源自胚胎大鼠颈上神经节的培养神经元的细胞核中。载体编码的血管加压素转录本也被分选到这些神经元的树突中，这表明树突mRNA转运的分子决定因素并非细胞特异性的。靶向元件的定位揭示了血管加压素mRNA中的两个片段，它们能够使通常局限于细胞体的α-微管蛋白mRNA实现树突区室化。
